[PATCH] Sanity check ops on loaded io engine

We require certain handlers to be there, or fio will either
malfunction or crash.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 03a2378..3817fc9 100644
--- a/fio.h
+++ b/fio.h
@@ -497,6 +497,7 @@
 /*
  * io engine entry points
  */
+extern int td_io_init(struct thread_data *);
 extern int td_io_prep(struct thread_data *, struct io_u *);
 extern int td_io_queue(struct thread_data *, struct io_u *);
 extern int td_io_sync(struct thread_data *, struct fio_file *);